Replaceable nose section for a marine propulsion unit

ABSTRACT

A replaceable nose section for a marine propulsion unit is disclosed. The marine propulsion unit includes a lower gear case that extends into the water and includes a lower portion that includes a shaft section, a prop section, and a nose section. The shaft section defines a first volume. The nose section includes an intermediate section that includes an intermediate bulkhead that defines a second volume. A nose cone is threaded to the intermediate section and defines a third volume such that the first and third volumes are not in fluid communication.

TECHNICAL FIELD

The present disclosure relates to a replaceable nose cone section for the lower portion of a marine propulsion unit.

BACKGROUND

Portions of a marine propulsion unit that extend into the water are susceptible to damage by underwater objects. The portions that extend below the hull of a marine vessel are especially susceptible, particularly the leading components such as the nose section. Therefore, the nose section should be designed to make replacement of the nose cone easier in the event of damage. Further, the design of the nose section should prevent oil from the gear case of the marine propulsion unit from leaking out should the nose cone become cracked. Similarly, the design of the nose section should prevent water from intruding into the gear case and causing severe damage to internal components should the nose cone become cracked.

U.S. Pat. No. 2,429,774 to SCHULTZ GEORGE E. et al., issued Oct. 28, 1947, entitled “Electric outboard motor,” discloses a housing that is threaded to receive a semi-spherically shaped nose. However, removal of the nose directly exposes the internal components. If the housing were filled with oil, the oil would have to be drained in advance of removing the nose. Further, if the nose were to become cracked from an impact, oil in the gear case would leak out. This would likely cause severe damage for the internal components. Similarly, if the nose were to become cracked from an impact, water would be allowed to intrude into the housing and cause severe damage for the internal components.

SUMMARY OF THE INVENTION

A marine propulsion unit is disclosed. The marine propulsion unit comprises a lower gear case having a lower portion comprising a shaft section defining a first volume and having an aperture on a front end, a prop section located abaft the shaft section, and a nose section located forward of said shaft section. The nose section comprises an intermediate portion defining a second volume and having an intermediate bulkhead, said intermediate portion being engaged to said aperture, and a nose cone defining a third volume and engaged to said intermediate portion wherein said first volume and said third volume are not in fluid communication.

In a second aspect of the current disclosure, a marine propulsion unit is disclosed comprising a lower gear case having a lower portion. The lower portion comprises a shaft section having a threaded aperture on a front end, a prop section located abaft the shaft section, and a nose section located forward of said shaft section. The nose section comprises an intermediate portion having an intermediate bulkhead, said intermediate portion being threadably engaged to said aperture, and a nose cone threadably engaged to said intermediate portion.

In a third aspect of the current disclosure, a torpedo-shaped section of a marine pod unit is disclosed. The torpedo-shaped section comprises a shaft section defining a first volume and having a threaded aperture on a front end, a prop section located abaft the shaft section, a nose section located forward of said shaft section. The nose section comprises an intermediate portion defining a second volume and having an intermediate bulkhead, said intermediate portion being threadably engaged to said aperture, and a nose cone defining a third volume and threadably engaged to said intermediate portion, wherein said first volume and said third volume are not in fluid communication.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view of three aspects of a marine propulsion unit installed on a marine vessel according to the current disclosure.

FIG. 2 is a cut-away view of a marine propulsion unit according to the current disclosure.

DETAILED DESCRIPTION

FIG. 1 shows a marine vessel 10 having a marine propulsion unit 20. The marine propulsion unit 20 includes a lower gear case 30 and a lower portion 60. The lower portion 60 includes a prop section 90, a shaft section 70, and a nose section 100. The lower portion 60 may be shaped into the form of a torpedo.

In one aspect of the current disclosure, the marine propulsion unit 20 is an outboard drive motor comprising an engine contained in an enclosure and a lower gear case 30 extending below the water and having a lower portion 60. The marine propulsion unit 20 is mounted to pivot on the transom of the marine vessel 10 to provide steering functions.

In a second aspect of the current disclosure, the marine propulsion unit 20 is a sterndrive comprising a gear box and a lower gear case 30 extending below the water and having a lower portion 60. The gearbox is connected to an engine via a driveshaft and transmits engine power at a generally 90-degree downward angle from the engine to the lower gear case 30. The marine propulsion unit 20 is mounted to pivot on the transom of the marine vessel 10 to provide steering functions.

In a third aspect of the current disclosure, the marine propulsion unit 20 is a pod unit, also known as an azimuth thruster. The pod unit comprises an upper pod unit and a lower gear case 30. The pod upper unit connects to the engine via a driveshaft and contains the transmission 50 and steering functions. The lower gear case 30 extends below the hull and is capable of rotating around 40 degrees to port or starboard in order to provide steering functions.

FIG. 2 shows the lower gear case 30 of a marine propulsion unit 20. The lower gear case 30 includes a strut 40 that extends below the waterline 15. The lower gear case 30 contains one or more driveshafts 200 for transmitting engine power to a propeller via at least one bevel gear set 270. The lower gear case 30 also includes bearings 260 for supporting the driveshaft 200 and prop shaft 205. The lower gear case 30 forms a first volume 140 that is at least partially filled with oil for lubricating the driveshafts 200, prop shaft 205, bevel gear sets 270, and bearings 260. The lower gear case 30 may also include an oil pump 250.

The lower portion 60 includes a nose section 100 in the front, a shaft section 70 in the middle, and a prop section 90 at the rear. The lower portion 60 may be torpedo-shaped. The shaft section 70 includes a drive shaft 200 for driving the prop shaft 205. If the marine propulsion unit 20 includes a rear prop 230 and an front prop 240, then the shaft section 70 may contain an inner prop shaft 210 and an outer prop shaft 220. A skeg 190 may be attached to the bottom of the shaft section 70. The skeg 190 may be of break-away type. The front of the shaft section 70 includes a circular aperture 80. The inside diameter of the shaft section 70 is formed with threads near the aperture 80 and is configured to threadably accept the intermediate portion 110.

The prop section 90 is located at the rear of the lower portion 60 and includes at least one prop 225 driven by a prop shaft 205. The prop shaft 205 is driven by a bevel gear set 270 driven by a driveshaft 200. In one aspect of the current disclosure, the prop section 90 may contain a rear prop 230 driven by an inner prop shaft 210 and an front prop 240 driven by an outer prop shaft 220. The inner prop shaft 210 and outer prop shaft 220 are driven by a bevel gear set 270 driven by a driveshaft 200. The use of both a rear prop 230 and front prop 240 increases the thrust provided by the marine propulsion unit 20. The front prop 240 may have three blades while the rear prop 230 may have four blades. The rear prop 230 may need to be smaller in diameter due to flow velocity at the blade tips. In order for the smaller rear prop 230 to have equal blade area to the front prop 240, the rear prop 230 may have four blades instead of three blades. In another aspect of the current disclosure, the front prop 240 may have four blades while the rear prop 230 may have five blades. The prop section 90 may also include a propeller shaft anode 50. The propeller shaft anode may have a parabolic shape that maximizes hydrodynamic efficiency while providing anti-corrosion protection.

The nose section 100 is generally bullet-shaped and located at the front of the lower portion 60 and includes an intermediate portion 110 and a nose cone 130.

The intermediate portion 110 is generally frustoconical and includes a first engagement portion on the outside diameter of a rear end and a second engagement portion on the outside diameter of a front end. The first engagement portion is configured to engage with the aperture 80. The first and second engagement portions may engage via a press-fit engagement, may be secured by a set screw or the like, or may be threaded. If the engagement is threaded, the intermediated portion 110 may include a threaded portion 170 on the outside diameter of a rear end and a threaded portion 170 on the outside diameter of a front end. The intermediate portion 110 also includes an intermediate bulkhead 120. The intermediate bulkhead 120 forms a fluid-impermeable wall. The intermediate portion 110, together with the intermediate bulkhead 120, forms a second volume 150. The intermediate portion 110 serves to prevent oil contained in the lower gear case 30 from escaping through the aperture 80. The threaded portion 170 on the rear end of the intermediate portion 110 is configured to engage with the threaded portion 170 of the aperture 80. Provisions are included for an o-ring 180 seal where the shaft section 70 and the intermediate portion 110 mate together.

The nose cone 130 is generally cone or bullet-shaped and defines a third volume 160. A threaded portion 170 on the inside diameter of the nose cone 130 is configured to engage with the threaded portion 170 on the front end of the intermediate portion 110. Provisions are included for an o-ring 180 seal where the nose cone 130 and the intermediate portion 110 mate together.

INDUSTRIAL APPLICABILITY

The lower portion 60 is located at the bottom of the lower gear case 30 and extends into the water and below the hull of the marine vessel 10. As such, the lower portion 60 is susceptible to damage from underwater objects such as rocks or shallows. The nose section 100, being at the front of the lower portion 60, is particularly susceptible to damage. Therefore, the nose section 100 of the current disclosure is configured with a nose cone 130 that can be replaced without draining the oil from the lower gear case 30.

A damaged nose cone 130 can be unscrewed from the intermediate portion 110. The intermediate bulkhead 120 contains the oil 35 in the lower gear case 30 while the nose cone 130 is being removed.

In the event of a severe crack in the nose cone 130, the intermediate bulkhead 120 serves to contain the oil 35 in the lower gear case 30 from leaking out before a repair can be affected. Preventing a loss of oil 35 prevents a damaged nose cone 130 from causing severe damage to the gears and bearings in the lower gear case 30. Similarly, the intermediate bulkhead 120 serves to keep water from intruding into the gear case 30 before a repair can be affected. Preventing water intrusion prevents a damaged nose cone 130 from causing severe damage to the gears and bearings in the lower gear case 30. 

what is claimed is:
 1. A marine propulsion unit comprising: a lower gear case having a lower portion, the lower portion comprising: a shaft section defining a first volume and having an aperture on a front end; a prop section located abaft the shaft section; a nose section located forward of said shaft section comprising: an intermediate portion defining a second volume and having an intermediate bulkhead, said intermediate portion being engaged to said aperture; and a nose cone defining a third volume and engaged to said intermediate portion; wherein said first volume and said third volume are not in fluid communication.
 2. The marine propulsion unit of claim 1 wherein the lower portion is torpedo-shaped.
 3. The marine propulsion unit of claim 1 wherein the lower gear case forms a portion of a strut that extends below the hull of a marine vessel
 4. The marine propulsion unit of claim 1 wherein said intermediate portion is threadably engaged to said aperture and said nose cone is threadably engaged to said intermediate portion.
 5. The marine propulsion unit of claim 1 wherein said prop section comprises front and rear counter-rotating props.
 6. The marine propulsion unit of claim 5 wherein the front prop has three blades and a first diameter and the rear prop has four blades and a second diameter that is less than the first diameter.
 7. The marine propulsion unit of claim 6 wherein the blade area of the front prop and the blade area of the rear prop are substantially the same.
 8. The marine propulsion unit of claim 5 wherein the front prop has four blades and a first diameter and the rear prop has five blades and a second diameter that is less than the first diameter.
 9. The marine propulsion unit of claim 8 wherein the blade area of the front prop and the blade area of the rear prop are substantially the same.
 10. The marine propulsion unit of claim 5 wherein a propeller shaft anode is threadably attached to a rear prop shaft.
 11. A marine propulsion unit comprising: a lower gear case having a lower portion, the lower portion comprising: a shaft section having a threaded aperture on a front end; a prop section located abaft the shaft section; a nose section located forward of said shaft section comprising: an intermediate portion having an intermediate bulkhead, said intermediate portion being threadably engaged to said aperture; and a nose cone threadably engaged to said intermediate portion.
 12. The marine propulsion unit of claim 11 wherein the lower portion is torpedo-shaped.
 13. The marine propulsion unit of claim 11 wherein the lower gear case forms a portion of a strut that extends below the hull of a marine vessel.
 14. The marine propulsion unit of claim 11
 15. The marine propulsion unit of claim 11 wherein said prop section comprises inner and outer counter-rotating props.
 16. The marine propulsion unit of claim 15 wherein the front prop has three blades and a first diameter and the rear prop has four blades and a second diameter that is less than the first diameter.
 17. The marine propulsion unit of claim 16 wherein the blade area of the front prop and the blade area of the rear prop are substantially the same.
 18. The marine propulsion unit of claim 15 wherein the front prop has four blades and a first diameter and the rear prop has five blades and a second diameter that is less than the first diameter.
 19. The marine propulsion unit of claim 15 wherein a propeller shaft anode is threadably attached to a rear prop shaft.
 20. A torpedo-shaped section of a marine pod unit comprising: a shaft section defining a first volume and having a threaded aperture on a front end; a prop section located abaft the shaft section; a nose section located forward of said shaft section comprising: an intermediate portion defining a second volume and having an intermediate bulkhead, said intermediate portion being threadably engaged to said aperture; and a nose cone defining a third volume and threadably engaged to said intermediate portion; wherein said first volume and said third volume are not in fluid communication. 